This invention relates generally to rings disposed in a ring retaining groove of a packing cup which is stationarily mounted over and around a reciprocally movable piston rod of a gas compressor. More specifically, this invention relates to a series of three such rings, first and second ones of which have piston rod oil scraping functions and a third of which has a gas sealing function to prevent gas from one side of the ring series from mixing with and contaminating lubricating oil pooled on an opposite side of the ring series and to prevent gas from escaping the compressor to ambient atmosphere.
Broadly speaking, numerous different types of both oil scraper rings and gas seal rings have long been known and used in the prior art. Examples of oil scraper rings known in the prior art include those used on pistons as disclosed in U.S. Pat. No. 4,103,594 granted to R. Geffroy on Aug. 1, 1978 and U.S. Pat. No. 4,473,232 granted to G. Umeha et al. on Sep. 25, 1984. There are also examples of oil scraper rings used in the prior art to remove oil from reciprocally movable piston rods such as that disclosed in U.S. Pat. No. 4,170,363 granted to U. C. Bergman on Oct. 9, 1979. Similarly, gas seal rings have long been known and used in the prior of the rod and past the seal ring to prevent mixing of gas with crank case lubricating oil, which not only results in loss of the, gas but also results in contamination of the oil. In fact, the gas seal ring shown in the preferred embodiment of the subject invention is, in and of itself, an example of a common prior art seal ring used on compressor piston rods.
Further, there is at least one example known to us in the prior art wherein one or more gas seal rings has been employed together with an oil wiper ring in a single circumferentially extending, radially outwardly opening ring retaining groove in a piston of an internal combustion engine. See U.S. Pat. No. 5,474,307 granted to R. De Biasse et al. on Dec. 12, 1995. However, the sealing rings of the patented arrangement are of the gas pressure energized type which require a gas pressure in the base of the groove of sufficient magnitude to force the scraper and sealing rings outwardly to engage and properly seal against a cylinder wall. It would be desirable to provide an oil scraper ring/gas seal ring arrangement for disposition in a single ring retention groove wherein the rings are spring compressed and not dependent upon gas leaking into the groove in order to force the rings into functional engagement with the rod. This is especially the case where the mixing of lubricating oil and compressed gas is to be avoided.
especially the case where the mixing of lubricating oil and compressed gas is to be avoided.
It is therefore an object of the invention to provide a ring assembly for a reciprocally movable compressor piston rod which functions to both scrape oil from the piston rod and provide a gas seal between high pressure gas on one side of the assembly and lubricating oil on the other side, which assembly is disposed in a single ring retaining groove of a packing cup stationarily mounted over and around the compressor piston rod.
It is another object of the invention to provide an oil scraper ring/gas seal ring assembly for disposition in a single groove of a compressor packing cup wherein the seal ring depends entirely upon the compression force of a garter spring for sealing against a piston rod.
It is also an object of this invention to provide a novel oil scraper/gas seal ring assembly for a single groove comprising a first oil wiper ring located on an oil filled crankcase side of the groove, a center oil scraper ring disposed next to the first ring and gas seal ring disposed next to the center ring on a gas compressor side of the groove.
It is a further object of the present invention to provide such a novel ring assembly wherein the center ring features a diagonally tapered outer peripheral surface portion which permits a compression spring disposed thereover to bear against the tapered portion and an adjacent sidewall of the first ring so as to both compress the center ring against a piston rod and to side load the first ring and center ring to form a thermal ring expansion gap between the first ring and the center ring and to urge the center ring against the seal ring so as to provide effective gas seals between opposing sides of the center ring and seal ring and between opposing sides of the seal ring and the groove.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and attached drawings, upon, which, by way of example, only certain specific embodiments of the invention are shown.